1. Field of the Invention
The present invention relates to a transmission control in a transmission system including a plurality of transmission lines.
2.Description of the Prior Art
In a loop transmission system (multi-loop transmission system) in which a plurality of loops or transmission lines are mutually connected, there has been known a transmission control method according to which all network control devices connected to the transmission lines all have the same structure, wherein communication of messages among the transmission lines is performed in accordance with the data content of the message without need for the aid of information about the loop configuration and the destination address of the receiving device. Reference may be made to U.S. Pat. No. 4,510,492 issued Apr. 9, 1985. According to this method, the message to be transferred between the loops or transmission lines can be easily altered, while the need for providing network control devices solely for the purpose of relaying message can be advantageously eliminated. However, in the application where the transmission lines are connected to constitute closed loops, a message once issued or generated undesirably may be continuously circulated along the closed loop.